1. Field of the Disclosure
The disclosure relates to a process for the beneficiation of titanium oxide-containing ores. More particularly the disclosure relates to a process for reducing the ore in a moving hearth furnace to form separable iron metal and titanium oxides. The disclosure additionally relates to a titanium and iron metallization product and the product of a process for the beneficiation of titanium oxide-containing ores. More particularly the disclosure relates to a titanium oxides and iron metallization product made by a process for reducing the ore in a moving hearth furnace to form separable iron metal and titanium oxides. The separated titanium oxide is useful as feedstock for producing titanium tetrachloride, titanium dioxide for pigment or other purposes or other refined, titanium-containing products.
2. Description of the Related Art
Moving hearth furnaces have been described for use in the reduction of iron oxide. Iron oxide to be reduced is charged to the rotary hearth furnace together with a source of carbon wherein the charge is exposed to reducing conditions to form reduction products comprising iron and slag.
In using a relatively pure iron oxide charge, reactivity of molten iron oxide slag with the interior surfaces of the furnace can be a concern. Consequently, that technology tends to use amounts of carbon sufficient for solid state reduction where there is rapid and substantially complete metallization of the iron oxide before the formation, if any, of a molten phase. Consequently, if and when the product of the solid state reduction is melted, there may only be a relatively small metal oxide fraction available to form the slag component. Additionally, since the iron metal represents the majority of the reduction product, large and easily recoverable iron granules form.
A carbon bed may be provided to protect the hearth from contact with the reacting charge. Since the carbon content of the charge is sufficient to provide rapid metallization, any minor proportion of ferrous oxides that might remain to react with the carbon bed would be an incidental and insignificant part of the process.
Instead of using a rotary hearth process to reduce substantially pure iron oxide, a rotary hearth process to reduce low grade ores such as ilmenite which contain iron oxide, high levels of titanium dioxide and metal oxide impurities has been proposed for making reduction products containing metallic iron and high grade titanium oxides such as synthetic rutile. However, reducing a low grade ore such as ilmenite which contains high levels of titanium dioxide and metal oxide impurities in a rotary hearth process poses processing challenges that are not encountered when reducing relatively pure iron oxide.
When conventional rotary hearth reduction technology is used to recover metallic iron and titanium oxides from low grade ores such as ilmenite, separating the small bits of iron metal which are distributed throughout the relatively high slag content is a problem. To solve this separation problem, a first pre-reduction step to metallize the majority of the iron oxide followed by a melting step, usually in an electric melter or intermediate hearth furnace, has been described for forming more readily separable molten iron that is relatively free of gangue and a slag that contains a high titanium oxides content. However, this multi-step process is a costly and energy intensive solution.
Mechanical separation of the numerous small bits of iron metal distributed throughout the slag is impractical because the bits of iron metal tend to be well below 50 microns in diameter. Since 50 microns is the lowest practical size limit for separation by sieving, most fine sieves having 400 wire per inch sieve which is the limit for sieving 50 micron diameter particles, sieving such numerous and small bits of iron metal is not a practical separation process. Magnetic separation also becomes impractical and inefficient for particles smaller than about 50 microns. Small bits of iron can be chemically separated but chemical separation adds significantly to costs.
There is a need for an energy efficient rotary hearth process for recovering easily separable metallic iron and titanium oxides from low grade ore reduction products.